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Characterization of airborne microorganisms: two indoor case studies.

Indoor Air '90, The 5th International Conference on Indoor Air Quality and Climate, Toronto, July 29 - August 3, 1990, 1990 Jul; :677-682

Link

NIOSHTIC No.

00227001

Abstract

The results of an evaluation of indoor air microorganism contamination in two office buildings were summarized. The study was part of an environmental evaluation of two buildings (building-A and building-B) in an east coast city whose employees reported symptoms consistent with the sick building syndrome (SBS). Building- A was a nine floor concrete structure and building-B consisted of two 12 story office towers joined by an enclosed three story shopping mall and office complex. The ventilation system of building-A consisted of 44 air handling units (AHUs) located in a penthouse and ten in the basement mechanical room. The ventilation system of building-B consisted of 119 AHUs. Air samples were collected in the two buildings using N-6 Andersen impactor samplers and analyzed for airborne bacterial and fungal species using standard counting methods. Airborne fungal concentrations in building-A and building-B varied from 3 to 110 and 7 to 130 colony forming units per cubic meter (cfu/m3), respectively. The building averages were 34 and 35cfu/m3, respectively. Over 40 different fungal species were identified. The average total fungal concentrations in the air outside building-A and building-B were 102 and 22cfu/m3, respectively. Penicillium, Cladosporium, and Aspergillus were the most frequently found species. Mesophilic bacteria concentrations in building-A and building-B averaged 44 and 56cfu/m3, respectively. The outdoor air bacteria concentrations averaged 80 and 31cfu/m3, respectively. Staphylococcus, Micropolyspora and Micrococcus were the most commonly isolated bacteria. Thermophilic actinomycetes were detected at low concentrations in both buildings, 13cfu/m3 in building-A and 18cfu/m3 in building-B. The authors note that despite having very different characteristics, the airborne microbial flora in the two buildings are very similar. Any observed differences are probably due to variations in the flora outdoors.